Brominated amorphous copolymers of ethylene and higher alpha olefins with amines



United States Patent BROMHNATED AMUHQUS CGP-JLYMERS (ll ETHYLENE ANDHEGHER ALPHA @LEFiNfi WITH AMINES Henry g. Malrowsld, Roselle Bath, andCharles W. Seclbach, Cranford, NJ assignors to Esso Research andEngineering Company, a corporation of Delaware No Drawing. Filed Jan.13, 1953, Ser. No. 708,370

6 Claims. (Cl. 260-88.2)

This invention relates to the preparation of brominated copolymers. Moreparticularly, the invention relates to the preparation of brominatedrubbery amorphous copolymers of ethylene and higher alpha olefins and tothe preparation of synthetic rubbers therefrom.

The preparation of amorphous rubbery copolymers of ethylene and higheralpha olefins by the low pressure polymerization process is described incopending application 672,435, filed July 17, 1957.

It has now been found that amorphous rubbery copolymers of ethylene andhigher alpha oletins can be brominated to form brominated copolyinerswhich then can be treated with certain curing agents to form syntheticrubbers having excellent mechanical, dynamic and aging properties. i

The amorphous rubbery copolyrners of ethylene and higher alpha olefinsused to form the brominated copolymers and the corresponding syntheticrubbers of the invention contain from 5 to 95 mol percent, preferably 30to 70 mol percent of ethylene with 95 to 5 mol percent, preferably 70 to30 mol percent of an alpha olefin containing 3 to 6 carbon atoms, have atensile strength in the range of from 2 to 500 p.s.i., a melting pointbelow about 50 C., a solubility in xylene at 100 C. greater than 15 wtpercent, an apparent modulus of elasticity at 50 C. of less than 1 10psi, a crystallinity of less than 10% as shown by X-ray analysis, and amolec ular weight of from 5,000 to 500,000. hese copolymers can beprepared by any known process, such as the low pressure polymerizationprocess or the high pressure polymerization process; see e.g. BelgianPatent 533,362, Chemical and Engineering News, April 8, 1957, pages 12through 16, Petroleum Refiner, December 1956, pages 191 through 196 andcopending application 672,435, filed July 17, 1957. Ethylene-propylenecopolymers are preferred due to their low cost. These amorphous rubberycopolymers do not contain su'flicient unsaturation to enable them to becured by conventional curing agents Such as sulfur or resins. lso, thesecopolyiners contain such a slight amount of unsaturation that theycannot be brominated to any appreciable extent by the addition ofbromine across their double bonds.

Surprisingly therefore, it was discovered that these copolymers can bebrominated when the bromination is carried out in solvents which arecapable of dissolving or swelling the copolymer and which do not reactrapidly with the brominating agent. Satisfactory solvents are aliphaticand aromatic hydrocarbons and their halogenated derivatives, such asn-heptane, benzene, chloroform, carbon tetrachloride, ethylenedichloride, and chloroben- Zene; with carbon tetrachloride andchlorobenzene being particularly preferred because of their excellentsolvent power and nonreactivity with the brominating agents.

The bromination of these copolymers is carried out by treatment of thecopolymer in an appropriate solvent with a brominating agent which ispreferably elemental bromine, although other bromine-ting agents such asN-bromosuccinimide can also be used. In particular, the bromination ofthe copolymers is carried out by first preparing a copolymer solutionhaving from 20 to 150 grams of copolymer per liter of solvent,preferably from 80 to 100 grams of polymer per liter of solvent, andthen treating the copolymer solution with a brominating agent. Thebrominating agent is employed in quantities which will producebrominated copolymers having from 1 to 50 wt. percent bromine,preferably 1 to 10 wt. percent and more preferably from 1 to 5 wt.percent bromine therein. The amount of brominating agent used iscalculated on bromination. If bromination takes place to an extent lessthan 100%, the quantity of brominating agent is adjusted to obtainbrominated copolymers having the desired amount of bromine therein. Thebromination is carried out at temperatures of from 20 to C. preferably75 to 110 C. The brominated copolymers are then isolated by standardtechniques known to the art.

The curing agents which react with the brominated copolyniers to formthe synthetic rubbers of the invention are metal salts, metal oxides,metal powders, amines and polyamines. in general, the metal componentsof the metal salts, metal oxides, and metal powders are chosen fromgroups HA, KB of the periodic table, and tin, copper and iron.Particularly useful are the metal oxides, sulfides, nitrates,phosphates, sulfates, and organic acid salts of groups HA and 11B metalsparticularly Zn, Cd, Mg, iron and lead. Also particularly preferred areamines and polyamines; in particular, any diamine, triamine, and higherpolyarnine having one or more of the following types of amino groups;(a) unsubstituted amino groups, (b) mono-substituted amino groups, (c)disubstituted amino groups, and (d) heterocyclic amines such aspyridine. The substituents on the monoand disubstituted amino groups areone or more of alkyl, aryl and heterocyclic groups. An added advantagein using these polyarnines is that they not only effectively produce thecured copolymers of the invention but they also act as antioxidants andstabilizers.

The reaction between the brominated copolymers and the curing agent iscarried out by mixing from 1 to 40 parts, preferably 5 to 20 parts, andmore preferably 5 to 10 parts by weight of a metal salt or oxide with100 parts by weight of copolymer. When the compound is a polyarnine,from 0.5 to 15 parts, preferably from 1 to 8 parts, and more preferablyfrom 2 to 6 parts by weight of polyamine per 100 parts by weight ofcopolymer is used. The reaction temperature employed is in the range offrom 225 F. to 350 F. preferably 280 to 320 F. and more preferably about310 F.

Fillers such as carbon blacks, silica, mica, various clays and the likecan be used, and in general their use is preferred. From 5 to parts,preferably 30 to 60 parts of filler per 100 parts of polymer is used.Highly desirable cured copolymers are prepared with 50 parts of carbonblack per 100 parts of copolymer. A wide variety of carbon blacks can beemployed as fillers, e.g. furnace black channel blacks, thermal blacks,lamp blacks, acetylene blacks and the like.

The reaction is carried out by mixing the brominated copolyrner, thecompound adapted to react with the bro minated copolymer, and thefiller, if any, in a rubber mill and heating the mixture to reactiontemperature. The mixing can also be carried out in other rubbercompounding equipment such as Banbury mixers or kneaders.

The invention will be better understood from the followin examples. Itis to be noted that values given in the examples and tables for tensilestrength and elongation are measured on 20-25 mil thick micropads unlessotherwise noted.

EXAMPLE I 90.0 grams of an ethylene-propylene copolymer having theproperties shown in Table I were mixed with 1.4 liters of CCL, in a3-liter 3-necl; flask. The mixture was heated to 70 C. with stirring,which was continued at this temerature until a homogeneous paste. wasobtained. There egos 1,1 15

Examples IX to XIV relate to the curing of the brominated copolymers ofthe invention with polyamines.

EXAMPLE IX nitrogen was bubbled through the reaction mixture to 5 100 g.of the brominated copolymer prepared by the facilitate the removal ofhydrogen halide, which was prcbprocess of Example I, which contained10.35 wt. percent ably a mixture of HCl and HBr. Then a vol me ofhalogen was mixed with 50 g. of carbon black on a warm acetone equal tothe volume of the reaction mixture was rubber mill. 2 g. ofm-phenylenediamine was then added added to the reaction mixture,resulting in precipitation of to the polymer mixture at roomtemperature. The mixthe copolymer which was then isolated, thoroughlyWashed, ture scorched badly during IIliXiIl". From this it can andkneaded with acetone. The copolymer was then be seen that brominatedpolymers having halogen conbanded on a warm mill, partially dried,formed into a tents above 10 wt. percent are diflicult to process whensheet, and dried under vacuum at 50 C. The solid 00- amines andpolyamines are used as curing agents. Spepolymer product weighed 95.5grams and contained 10.35 cial precautions are required to preventscorching of high Wt. percent halogen (Paar determination). Some of thebromine content copolymers. halogen present was chlorine, which wasintroduced into the copolymer by reaction involving the COL; diluent.EXAMPLES XTHROUGH XII Evaporation of the mother liquor from the reactionleft The brominated copolymers of Examples VI, VII and as a resldue 4-1g. Of a O ly cop lymer. The PIOP S VIII respectively were treatedaccording to the process of of the bromrnate'd copolymer, the reactionconditions, and E l IX ith i he curing mixture A hi h i the propertiesof the unsubstituted copolymer are listed posed of 100 parts brominatedcopolymer, 4 parts min Table I. phenylenediamine, and 4 parts stearicacid, or curing mix- EXAMPLES H THROUGH VIII ture B which is composed of100 parts brominatcd copolymer, 50 parts carbon black, 4 partsm-phenylenediarnine, Copolymers having the properties and compositionsand 4 parts stearic acid. The curing mixture used, the shown in Table Iwere brominated by the procedure of conditions of cure, and theproperties of the cured copoly- Example I using the quantities orreactants and reaction mers are also given in Table II. Additionally,the propconditions given in Table I. erties of the correspondingbrominated copolymers and Table I I II III 1V V VI VII VIIIEthylenepropylene copolymcr used:

Mole percent propylene 14.1 9. 2 9.1 42 15 42 42 42 Inherent viscosity,i 1.75 1. 42 1. 1.86 1.06 1. 4S 1. 48 1. 48 Tensile strength, p.s.i---128 170 630 145 123 285 285 285 Elongation, percent 660 360 180 444 66080 80 80 Softening point, C 52 20 31 31 so 30 30 30 Melting pooint, C s234 75 5s 70 30 30 30 Reaction conditions:

Solvent CO1; CC]; (3C1; 00110 CcHu Cal I0 CoHu Total volume, ml 15001500 1500 1200 1200 1500 1500 1500 Copolymcr, grams 90 100 100 70 70 100100 100 Copolymcr c0110., g./1 67 67 58 58 07 67 67 Bromine, g 30.0 11.129.1 22.4 15.0 30.0 20.0 10.0 Temperature, C 7 7 70 70 70 70 70 Reactiontime, hr 4.5 3 5 6.5 1 2 5.5 3. G7 3.5 Product:

Total copolymer, g 90.6 100.4 103.7 75.6 77.7 101.9 09.9 102.8 Percentyield 05 05 03 so 00 0s Oily copolymcr 4.1 4.4 6.1 2.4 1.2 4.7 4.6 6.5Brorniuatcd copolymcn- 95. 5 96. 0 97. 6 73. 2 76, 5 07. 2 95. 3 96. 3Inherent viscosity, 1 1' 1.03 0. 871 0.517 1.00 1. 00 0.002 1.27 1. 25Halogen, weight percent 8 3 10. 35 3 0.93 4 8.77 5 4. 96 5 2. 93 5 5. 7G5 1. 80 l 2. 30

1 In tatralin at 125 C. at a concentration of 1 g./litcr for the solidcopolymer only. 1 Based on assumption that the bromine present reactscompletely with all the copolymer present and only by substitution.

3 Paar bomb determination.

a Dictert determination: 1.37 Weight percent chlorine and 7.40 weightpercent bromino.

5 Dietort determination. 5 Of solid copolymer. 7 0n the soluble portionof the solid copolyrncr. n-lieptanc.

It can be seen from Table I that amorphous copolymers can besuccessfully brominated using a wide variety of reaction conditions andsolvents.

the corresponding unbrominated copolymers from which the brominatedcopolymers were prepared are also given in Table II for comparisonpurposes.

Table II X XI XII Tensile Elong- Tensile Elong- Tensile Elongstrcngth,ation, strength, atlon, strength, atlon,

p.s.1. percent p.s.i. percent p.s.i. percent Unbrominatcd copolymer- 28580 285 80 285 80 Brominatcd copolymer- 251 108 232 160 223 116 Curingmixture A:

310 510 70 580 790 530 420 00' at 310 F 430 00 620 620 050 380 S0 at 310F 560 635 300 120 at 310 F 480 645 430 Curing mixture 13:

30 310 F l, 470 1, 340 380 00 at 310 F 1, 1,490 420 00' at 310 F 1, 6201,500 430 at 310 F 1, 5-10 1, 510

It can be seen from the above table that the physical properties of thepolyamine cured brominated copolymers are markedly improved compared tothose of both the unbrominated and the brominated copolymers. Also, itcan be seen that the addition of carbon black to the curing 5 mixture(as is in curing mixture B) is highly advantageous.

EXAMPLES XIII AND XIV Brominated copolymers were prepared from amorphousethylene-propylene copolymers by brominating the latter in benzeneaccording to the process of Example I. The properties of theseunbrominated and brominated copolymers are given in Table III.

Table III XIII XIV-- Bromin- Unbro- Brominated minated atedcopolycopolycopolymermer mer Inherent viscosity, vi- Softening point, 0Melting point, O- Tensile strength, p.s

Elongation, percent 80 130 220 Apparent modulus of elasticity, p.s.i.

1. 05 1. 09 Bromine, weight percent 0 3.03 4.

The corresponding unbrominuted copolymer is a blend of threeethylene-propylene copolymers having the following properties:

Grams Tensile Elonga- Inherent 35 Copolymer inblend strength, tion,viscosp.s.i. percent ity, vi

Portions of the above brominated copolymers were used to prepare thefollowing curing mixtures:

Curing mixtures A and B-Compositions as shown for Examples X throughXII.

Curing mixture C: Parts Brominated copolymer 100 The above curingmixtures were prepared by mixing the components in a cool rubber mill(the stearic acid was added before the polyamine). The mixtures werethen cured. The tensile strengths and elongation for the curedbrominated copolymers are given in Table IV together with the tensilestrengths and elongations of the corresponding brominated andunbrominated copolymers for comparison purposes.

Table IV Example XIII Example XIV Tensile Elonga- TensileElongastrength, tion, strength, tion,

p.s.i. percent p.s.i. percent Unbrominated copolymer 570 Brominatedcopolymer 420 130 290 220 Control:

30 510 60'.-. 340 470 270 Ouringm ture 30' at 308 F. 755 220 795 265 840240 830 250 1, 750 200 1, 840 1, 910 240 Curing mixture E:

30 at 308 F- 1, 380 60 60 at; 308 F 1, 970 90 1, 670 100 l, 710 70 1,580 70 90 at 308 F 1, 820 70 It can be seen from the data in Table IVthat the brominated copolymers of the invention are cured successfullyby various polyamines to rubbers having high tension strength andelongations. The addition of fillers such as carbon black to the curingmixtures provides products after curing which have even higher tensilestrengths.

Examples XV through XXIII are examples of brominated copolymers curedwith either metal salts or metal oxides. I

EXAMPLES XV THROUGH XXII The prominated copolymers prepared in ExamplesI, III, V, VII, VIII and VI were cured using the curing mixtures andconditions listed in Table V for Examples XV through XX respectively.The brominated copolymer of Example XXI was prepared by brominating anamorphous ethylene-propylene copolymer in benzene and had 0.03 wt.percent bromine and an apparent modulus of elasticity of 1.05 X10 p.s.i, at 50 C. The brominated copolymer of Example XXII was prepared bybrominating an amorphous ethylene-propylene copolymer in benzene and had4.35 wt. percent bromine and an inherent viscosity of 1.48. Thebrominated copolymers of Examples XV through XXII were formed intovarious curing mixtures and cured. The properties of the brominated andthe cured copolymers, the conditions of cure, and the curing mixturesused are given in Table V.

Carbon black 50 Curing mixture J Parts Curing mixture P: PartsBromlnated copolymer 100 Brominated copolymer 100 Zinc OX1de 5 Carbonblack.. 50 acld 1 Magnesium oxide.... 10

Curing nuxture K: 5 Curing mixture Q:

Bf'ommafed copolymer 100 Brominated copolymers 100 Zmc X1d 10 Carbonblack Steanc id 1 PbaQ1 Curing mixture L:

Brominated cgpolymer 100 10 It (I311 175 en fI' m the above table thatmarked 1m- Carbon b1ack 50 prov ment in tensile strength compared toboth the un- Cadmium sulfide 10 brominated and the brominated copolymerscan be ob- C in ixtu M; tained by treating the brominated copolymerswith as Brominated eopolymer 100 little as 5 parts of zinc oxide forvery short curing times, Carbon black 50 It was found that arelationship existed between desirable Zlnc ox1de 10 mechanicalproperties for the cured brominated copoly- Table V Xv XVI XVII XVIIIXIX XX XXI XXII '1.s., 13., T3, E 0 .3, T.S., E., 1.S., 13., 12s.,'I.S., 12., p.s.i. perp.s.i. perp.s.i perp.s.i. perp.s.i. perp.s.i. pcr-11.3.1. perp.s.i. percent cent cent cent cent ccut cent centUnbromiuatetl copolymeru 123 660 145 444 123 000 123 000 235 235 30 23530 235 30 Bromlnnted copolymer 230 230 232 130 223 116 251 103 420 130230 220 Curing mixture G:

15nt308F 1, 750 136 30at308 F 543 1,474 00'at303 F 520 1,429 90'3t30SF515 1,515 120' at 308 F 4 4 1,520

Curing mixture H:

30 at 303 F 390 503 1,249 '31", 303 F 972 472 1,324 90' at 303 F 4402,000 390 1,017 510 1,549 12033 303 F 1,213 536 1,503 Curing mixture I:

30' at 303 F-. 60' at 303 F 90' at 303 F 120' at 303 F Curing mixture J:

30' at 303 F 734 390 60 at 303 F 631 760 90et308 F 043 372 120' at 303 F315 304 Curing mixture K:

30 at 303 F 00' at 303 F 90' at 303 F 120' at 303 F. Curing mixture L:

3011330 00' at 303 F 90' at 303 F 120' at303 F Curing mixture M:

30' at 303 F 00' at 303 F 30' at 303 F 120' at 303 Curing mixture N:

30' at 303 30' at 303 F 90' at 303 F 120' at 303 F Curing mixture 0:

30' at 303 F 30' at 303 F 90m: 303 F 120' at 303 F Curing mixture P:

30' at 303 F 30' at 303 F 90' at 303 F 120' at 303 F i s l 1 1,070 30000' at 303 F 1,300 300 90' at 303 F 1,900 240 1 T.S.-Te11sile strength.1 E.Elongatlon.

Curing mixture N: mers and the inter-relation between the brominecontent Brominated eopolymer 100 of the copolymer and the curing time.In general, the Carbon black 50 higher the bromine content the shorterthe curing time Ferric oxide 10 required to produce cured copolyrnerswith excellent Curing mixture 0: V mechanical properties. It is to benoted that the data Brominated copolymer 100 given in all Of the abovetables where carbon black is Carbon black 50 a component of the curingmixture is given for semi- 10 reinforcing furnace carbon black. Othercarbon blacks Zinc sulfide-,

9 such as medium thermal carbon black and high modulus furnace carbonblack were also used and gave cured copolymers with excellent physicalcharacteristics. It can be seen from the above table that a largevariety of metal oxides and metal salts can be used as eiiective curingagents for the brominated copolymers.

A brominated ethylene-butene-l copolymer was also prepared by the abovebromination process. This co polymer can be cured to give a superiorsynthetic rubber in accordance with the invention.

EXAMPLE XXIII The brominated copolymer of Example XXI cured by curingmixture H was formed into two 6" x 6" pads using a 60 minute curing timeat a 308 F. curing temperature. The cured pads had the followingproperties.

Tensile strength 1200 p.s.i. Elongation, percent 430. Modulus/300% 740p.s.i.

Oven aged for 72 hours at 300 F.:

Tensile strength 900 p.s.i.

Elongation 300%.

Shore hardness 65.

Ozone resistance After 6 hours exposure to ozone, the pads Were stillsmooth and uncracked.

Dynamic modulus tests:

Percent relative damping 35.8.

Dynamic stiitness (K) 447x10 dynes/cm.

Internal viscosity (1 f) 1.315 10 poisescycles/sec.

As can be seen from the above example the cured copolymers of theinvention unlike natural rubber have excellent high temperatureproperties and ozone resistance due to the absence of any functionalgroups reactive to ozone. Additionally, they have the unusualcombination of high dynamic stifliness and low percent relative damping.In these properties they resemble GR-S and natural rubber. Accordingly,the cured copolymer of the invention are ideal for use in tire treadswhere resilience and stiffness characteristics are particularlydesirable.

It is to be understood that this invention is not limited to thespecific examples which have been presented for illustration purposesonly. Moreover, modifications of the invention can be made by thoseskilled in the art without departing from the scope and spirit of theinvention.

What is claimed is:

1. process for producing a synthetic rubber which comprises:

(1) reacting a copolymer of 5 to mol percent ethylene and 95 to 5 molpercent of a C C alpha olefin in an inert solvent selected from thegroup consisting of aliphatic and aromatic hydrocarbons and theirhalogenated derivatives, said solvent capable of at least partiallydissolving the copolymer, with a brominating agent at a temperature inthe range of 20130 C. to form a brominated copolymer having from 1 to 10weight percent bromine;

(2) isolating and drying said copolymer; and

(3) curing the dried brominated copolymer at a temperature in the rangeof 225 350 F. with an aromatic polyfunctional compound containing atleast one primary amine group as one of the functional groups.

2. A process according to claim 1 wherein the aromatic polyfunctionalcompound is Z-aminopyridine.

3. The process of claim 1 wherein the aromatic polyfunctional compoundis p-phenylene diamine.

4. The process of claim 1 wherein the aromatic polyfunctional compoundis 2,6-diarnino pyridine.

5. The process of claim 1 wherein the aromatic polyfunctional compoundis m-phenylene diamine.

6. The rubbery product of claim 5.

References Cited in the file of this patent UNITED STATES PATENTS2,183,556 Fawcett Dec. 19, 1939 2,200,429 Perrin et al. May 14, 19402,364,410 Wittaker Dec. 5, 1944 2,405,971 McAlevy Aug. 20, 19562,850,490 Canterino et al. Sept. 2, 1958 2,920,064 Baptiss et a1 Jan. 5,1960 FOREIGN PATENTS 478,513 Canada Nov. 13, 1951

1. A PROCESS FOR PRODUCING A SYNTHETIC RUBBER WHICH COMPRISES: (1)REACTING A COPOLYMER OF 5 TO 95 MOL PRECENT ETHYLENE AND 95 TO 5 MOLPERCENT OF A C3-C6 ALPHA OLEFIN IN AN INERT SOLVENT SELECTED FROM THEGROUP CONSISTING OF ALIPHATIC AND AROMATIC HYDROCARBONS AND THEIRHALOGENATED DERIVATIVES, SAID SOLVENT CAPABLE OF AT LEAST PARTIALLYDISSOLVING THE COPOLYMER A BROMINATING AGENT AT A TEMPERATURE IN THERANGE OF 20*-130*C. TO FORM A BROMINATED COPOLYMER HAVING FROM 1 TO 10WEIGHT PERCENT BROMINE; (2) ISOLATING AND DRYING SAID COPOLYMER; AND (3)CURING THE DRIED BROMINATED COPOLYMER AT A TEMPERATURE IN THE RANGE OF225*-350*F. WITH AN AROMATIC POLYFUNCTIONAL COMPOUND CONTAINING AT LEASTONE PRIMARY AMINE GROUP AS ONE OF THE FUNCTIONAL GROUPS.